Publications

Abstract The observation of a micellar cubic phase is reported for a mixture of an antimicrobial peptide from the Lactoferrin family, LFampin 265-284, and a model membrane system of dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (3:1), as derived from small-angle x-ray diffraction (SAXD) measurements. The system shows remarkable thermotropic polymorphism: the peptide disrupts the lipid bilayer, forming a cubic phase of the space group Pm 3n (t < 28 degrees C), and as the temperature increases it shows a complex phase behavior (not fully clarified by SAXD). The onset, volume fraction of each phase, and phase parameters are seen to vary with peptide/lipid ratio and temperature. The obtained SAXD data represent the first experimental evidence, to our knowledge, of a micellar cubic phase in the context of antimicrobial peptide/membrane interaction. We propose that the micellization of the membrane according to the carpet model, for long proposed as a possible mechanism of action, can go through the formation of a cubic micellar phase.

Abstract Food-grade galacto-oligosaccharides (GOS) are commercially available as transparent syrups or dried powders Food powders can be found in an amorphous metastable state which is very sensitive to changes in temperature and moisture content In this work the impact of water content on thermal behavior and relative humidity on water sorption behavior of amorphous GOS powders were studied Results from differential scanning calorimetry (DSC) and sorption Isotherms suggest that GOS mixture studied with high content of oligosaccharides has low ability to crystallize A dramatic decrease in the stability of GOS powders occurred above critical water content (12-14 g/100g) and corresponding critical water activity (0 55-0 62) Above these conditions GOS powder lost its amorphous character collapsed and shrank as the powder became a transparent solution-like material The knowledge about the physicochemical changes acquired during the present study should be used to a proper control of processing and storage conditions to achieve and maintain optimum powder quality with desired properties

Abstract The standard massic energy of combustion, in oxygen, of the crystalline 9-anthracenecarboxylic acid was measured, at T=298.15 K, by static-bomb combustion calorimetry, from which the standard molar enthalpy of formation, in the condensed phase, was calculated as Delta(f)H degrees(m)(cr) = -(267.3 +/- 3.4) kJ . mol(-1). The standard molar enthalpy of sublimation of this acid, at T=298.15K, Delta(g)(cr)H degrees(m) = (139.4 +/- 0.9) kJ . mol(-1), was determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. From the data presented above, the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived, Delta(f)H degrees(m)(g) = -(127.9 +/- 3.5) kJ . mol(-1). The experimental result is interpreted in terms of enthalpic increments, molecular structure and compared with structurally similar compounds.

Abstract In the title compound, C42H29Br, the dihedral angles between the central benzene ring and the three attached benzene rings are very similar, lying in the range 52.65 (6)-57.20 (7)degrees. Of the dihedral angles between the rings of the o-biphenyl substituents, two are similar [46.34 (7) and 47.35 (7)degrees], while the other differs significantly [64.17 (7)degrees]. In the crystal, molecules are linked into centrosymmetric dimers by two weak C-H center dot center dot center dot pi interactions.

Abstract Swimming pool water requires disinfection in order to protect swimmers frompathogenic microorganisms. However, disinfection has also unintended consequences.Chlorine, the most commonly used disinfectant, reacts with the organic matter (natural,human and synthetic) present in the pool water producing disinfection by-products(DBPs) which are of primary concern. Currently, more than one hundred DBPs havebeen identified in swimming pools including, trihalomethanes, haloacids, halonitriles,haloaldeydes, haloketones, halonitromethanes, haloamines, haloamides, haloalcohols andhalogenated UV filters. Some of these DBPs have been detected in the blood, alveolar airand urine of swimming pool attendants. Exposure to DBPs has been linked to adversehealth effects, like increased risk of asthma and other respiratory diseases as well asbladder cancer. Very recently, the genotoxicity and mutagenicity of swimming poolwater have been assessed. It has been found that the mutagenicity of pool waters wassimilar to that of typical drinking water, indicating that the levels of mutagenic DBPs aresimilar in both waters.

Abstract Tamoxifen is a nonsteroidal antiestrogen that is currently and widely used in the treatment of breast cancer in all of its stages, in adjuvant therapy as a long-term suppressant of tumor recurrence and also as a chemopreventive agent in women that are in high risk of developing this type of estrogen-dependent cancer. From a toxicological and (bio)analytical point of view the knowledge of the metabolic pathways of a drug is found to be extremely important. So, in the present work the most important tamoxifen biotransformation steps were reviewed in the light of recent pharmacological data. This overview also includes the current controversy concerning tamoxifen DNA-damaging (genotoxic) versus non-genotoxic mechanisms. A special focus will be given to the putative application of electrochemical methods as a modern and reliable analytical tool for determination of tamoxifen and its metabolites. Moreover, the potential of DNA electrochemical sensors for detection of structural damage to DNA as a basis for toxicity screening is highlighted. Future prospects looking for the importance of developing new analytical methodologies are also discussed.

Abstract Luciferase is a powerful tool in bioanalysis. Several well-established methods employ luciferases, particularly firefly and Renilla luciferases, as reporter genes or biosensors in environmental, biomedical and biochemical research. These techniques have interesting features for the analyst such as sensitivity, specificity and reduced assay time. Nanochemistry and Nanotechnology are disciplines that are gaining much attention and evolving rapidly. They allow the development of custom-made nanomaterials with the desired properties, starting from conventional bulk materials. Recently, the coupling of nanomaterials such as carbon nanotubes, mesoporous silica nanoparticles, metallic nanoparticles and quantum dots with luciferases led to new or improved methodologies for analyte quantification and enhanced gene delivery strategies. One of the principal scopes is to modulate or alter luciferase's bioluminescence emission, either by stabilizing it or tuning it to longer wavelengths. This chapter aims to present state-of-art articles regarding new methods based on the coupling of luciferases to nanomaterials, along with a brief introduction to Nanoscience.

Abstract The asymmetric unit of the title compound, C18H21N3S, contains five molecules. The equivalent bond distances in the five molecules are in excellent agreement, the r.m.s. fit being within 0.007 angstrom. The five molecules are linked into a chain consisting of alternating pseudo-enantiomers by N-H center dot center dot center dot S hydrogen bonds supplemented by weak C-H center dot center dot center dot pi interactions. The action of a glide plane links the asymmetric unit into an extended chain. A polymorph of the title compound with one molecule in the asymmetric unit was reported by Braun et al. [Cryst. Res. Technol. (1988), 23, 35-39].

Abstract The thermodynamic study of the phase transition (fusion and sublimation) of 2,2':5',2 ''-terthiophene and 3,2':5',3 ''-terthiophene is presented. The obtained data is used to evaluate the (solid + liquid) and (solid + gas) phase equilibrium, and draw the phase diagrams of the pure compounds near the triple point coordinates. For each compound the vapour pressures at different temperatures were measured by a combined Knudsen effusion method with a vacuum quartz crystal microbalance. Based on the previous results, the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived at T = 298.15 K. For the two terthiophenes and for 3,3'-bithiophene, the temperature, and the molar enthalpies of fusion were measured in a power compensated differential scanning calorimetry. The relationship between structure and energetics is discussed based on the experimental results, ab initio calculations and previous literature data for 2,2'-bithiophene and 3,3'-bithiophene. The 3,2':5',3 ''-terthiophene shows a higher solid phase stability than the 2,2':5',2 ''-terthiophene isomer arising from the higher cohesive energy due to positioning of the sulphur atom in the thiophene ring. The higher phase stability of 3,3'-bithiophene relative to 2,2'-bithiophene isomer is also related to its higher absolute entropy in the solid phase associated with the ring positional degeneracy observed in the crystal structure of this isomer. A significant differentiation in the crystal phase stability between isomers was found.